Add paint brush parameter tests

docs/modernization/build-inventory.md

@@ -81,8 +81,8 @@ Known local toolchain state:
   `pp_paint`, `pp_document`, `pp_renderer_api`, `pp_paint_renderer`,
   `pp_ui_core`, `pano_cli`, and their current headless test binaries,
   including foundation event/logging/task queue coverage, PPI header, settings
-  document, paint stroke sampling, UI color parsing, and layout XML parse
-  coverage.
+  document, paint brush/stroke coverage, UI color parsing, and layout XML
+  parse coverage.
 - `panopainter_validate_shaders` validates the current combined GLSL shader
   files for one vertex stage marker, one fragment stage marker, valid marker
   order, and existing relative includes.